1. Field of the Invention
The present invention relates to a quantum cascade semiconductor laser.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-526214 (hereinafter referred to as Patent Document 1) discloses a quantum cascade laser (QCL) and a method of manufacturing the same. The quantum cascade laser has a buried heterostructure (BH) in which a mesa waveguide including a core layer is buried with an electrically insulating layer. The electrically insulating layer is made of a semi-insulating material such as iron-doped indium phosphide (Fe-doped InP).